Polymeric coatings are applied as liquids to a wide variety of substrates. The coatings can be applied for a variety of reasons, for example, as protective coatings, decorative coatings, sealants, for insulation properties and/or to modify surface characteristics of the substrate to the surface characteristics of the coating.
In general terms, coatings applied as liquids comprise three primary components: pigment; binder; and, solvent. In this context, the term “pigment” is used to refer to non-film forming components. The term “binder” is used to refer to those materials that form the film, i.e. solid materials that provide the protective and/or functional coating. The third component (solvent) is a fugitive material that functions as a dispersing medium for the pigment and binder solids, and is a carrier for transporting the solid materials to the substrate. Once the coating has been applied, it is generally desirable to rid the applied coating of its carrier solvent as quickly as possible. For many coatings, the removal and carrier solvent trigger some form of film forming process and involves the evaporation of the solvent to the atmosphere. When the carrier solvents are organic in nature, they generally contribute to environmental problems (i.e. VOC levels and issues with VOC regulations). Of course when water is used as a solvent, VOC problems are reduced.
In the construction industry, protective and/or decorative coatings are applied to foundations, walls, roofs and various structures. The materials or substrates involved can comprise a variety of materials, for example masonry, cement, concrete, wood, fiber board, plaster, plaster board, metal, brick, paper, plastic, rubber, glass, asphalt and/or foam (e.g. styrene foam or polyurethane foam). The substrate being coated may comprise portions of more than one type of material. Some of the substrates can be quite irregular or porous, and thus difficult to coat. The substrates may be horizontal, vertical or of a variety of alternate configurations, or of complex shape and/or orientation.
Different issues may be presented, depending on the location and purpose of the substrate. For example, below grade structures (below ground level walls) often are subject to hydrostatic pressures from groundwater. The type of compositions applied as coatings to such structures may be intended, therefore, to provide both a good water barrier and a good vapor tight barrier.
Above grade exterior structures (for example above ground level exterior walls) are subject to weather and weathering effects, but it may also be desirable that they be configured to “breathe”, i.e. allow passage of water vapor therethrough, to allow internal wall regions to dry.
Issues with formulation and application of protective coatings to a wide variety of substrates concern such variable factors as: environmental conditions during application; drying time issues; coating thickness issues; application conditions; and, logistical issues. Environmental conditions, for example, can relate to whether the coating is applied in an internal closed environment, or an external, outside, open environment. Coating thickness issues can relate to how thick the coating application needs to be, to be effective for the intended result and to manage structure variations, when the substrate has surface variations or irregularities. Issues also relate to the propensity of coatings, applied to vertical surfaces, to slough, sag or wash off prior to full cure or set up. Application condition issues can relate, for example, to: weather conditions, especially if exterior application is involved; humidity conditions; and/or dust conditions. The logistical issues can concern such factors as: whether specialized personnel or equipment are needed for application; potential disruption of construction site processes during application; selecting and waiting for appropriate temperature/weather/environment conditions for application of the coating and set up; in some instances a need for tenting the region to be coated, and even using heaters for the tented region; and, related logistical issues that concern construction costs, timing and delay issues.
In addition, a variety of issues can relate to the carrier fluid for the coating. That is, the coatings are typically applied from suspension or solution, i.e. in the form of flowable liquid. Organic solvents or carriers can create health and/or environmental issues: during application and carrier fluid evaporation; and/or during formulation, handling and storage. Aqueous carriers can raise issues with respect to maintaining composition integrity during handling, storage, and application; and, greater sensitivity to: environment conditions such as weather (temperature and/or humidity) during application and water evaporation (drying).
As a practical commercial matter, compositions and techniques developed for coatings that are formulated for application to construction materials and surfaces, need to be developed to manage wide variations in the above variables. Indeed, in formulating compositions for application, for example at construction sites, such variables as: substrate material type; substrate surface orientation; interior/exterior applications; and, any temperature/humidity variations; etc, are preferably managed so that a selected coating composition is satisfactory for as wide a variety of situations posed by these variables, as reasonable. That is, it is not, as a practical matter, desirable to need to specifically formulate a composition that is dependent on too many of the above variables in the field. Rather, it is desirable to provide a minimal number of coating compositions that are applicable to a wide variety of substrates under a wide variety of circumstances, for effective practical commercial application.
In addition, it is desirable to formulate coatings that do not require special, difficult to manage, handling application techniques in the field, to the extent reasonable, so they can be applied by a wide variety of application personnel without highly developed, specialized, knowledge. That is, a commercial composition that is intended to be successful, for wide and extensive use, is preferably one for which special on-site supervision during handling and application is not required, but rather which is formulated to be appropriate for effective application by personnel with a limited amount of necessary background, training and supervision.
Coating formation in thick film applications, when needed and intended, has raised significant issue in the context of coatings for construction materials and similar applications. Especially when applied as a thick wet film, film distortion and integrity loss can occur with resulting blistering, puckering and/or other flaw formation during cure or film set up. Also sagging and sloughing can affect resulting dry film integrity further, and with thick films initial adherence issues can be exaggerated. These variables are preferably managed by the formulator of the composition, so that in field applications undesired levels of problems are avoided.
In addition, cost factors are of significant concern. It is desirable that the formulation be developed with materials such that composition costs and application costs are not unacceptable burdens for the construction projects involved. Also, variations in construction specification and regulation issues need to be met in a variety of jurisdictions for a variety of projects, by a commercial composition, for it to be effective. Thus, the materials used are preferably materials of known property and characteristic, so that extensive environmental and health evaluations are not required for the product to be accepted.
These and other issues are of concern, when developing compositions for wide construction and construction material application, and are taken into consideration by such companies as Protective Coatings Technology, Inc. of Menomonie, Wis., 54751 (now part of Polyguard Products Inc, of Ennis, Tex., a provider of such products). The present application provides compositions, composition formation techniques and methods of practical application to address the issues identified above, on a useful, commercially practical, scale. It is noted that the techniques can also be applied in a wide variety of alternate applications not necessarily involving construction sites and materials.